Encapsulated solenoid operated valve assembly

Abstract: A solenoid valve assembly comprising solenoid windings (44) positioned around a central core (56) and a movable valve element (82) arranged on the axis of the windings, the windings being supported by a spindle having a boss (20) adapted to be received in an opening formed in a body at one end of the spindle and a fluid fitting (42) adapted to establish a connection with a pressure line at the opposite end of the spindle, and sealant structure for sealing the interior of the spindle from external contaminants including an encapsulation material (46,48,50) surrounding the spindle and the windings.

Description: The present invention relates to a solenoid valve assembly and to a process of manufacturing the same. DE-U-0812707 generally discloses a solenoid valve assembly comprising a spindle with a central opening, a movable valve element in said opening, an electric coil surrounding said central opening; a fluid fitting at one end of said opening, a mounting boss at the other end of said opening; a valve orifice in said spindle adapted to register with said valve element when said coil is deenergized, said valve element and said valve orifice thereby providing controlled fluid flow through said central opening; and an encapsulation enclosing said spindle. According to one aspect of the present invention as claimed, the aforesaid generally disclosed solenoid valve assembly is characterized in that a sealant material surrounds said spindle and the encapsulation compresses the sealant against said spindle, thereby hermetically sealing said coil. According to another aspect of the present invention, there is provided a process for manufacturing a solenoid valve assembly comprising moulding a spindle from nylon material, winding electrical windings around said spindle, enclosing said windings in a housing; applying a silicone sealant in liquid form to said spindle at one axial side of said windings; curing said sealant with ultraviolet light to harden the sealant; placing said spindle and said windings in a mould; injecting nylon material into said mould thereby surrounding said windings and said spindle with nylon and encapsulating said windings and said spindle upon injection of said nylon material into said mould as said nylon material compresses said sealant against said spindle. A solenoid valve assembly in accordance with the invention has the advantage that the compression of the sealant against the spindle by the encapsulation produces a permanent barrier between the spindle and the encapsulation material thereby improving the sealing of the coil from the environmental conditions and hence increasing the durability of the assembly. The solenoid valve assembly of the present invention may be adapted especially for controlling transfer of a pneumatic fluid, such as air, in an automatic air suspension system for an automotive vehicle. The solenoid valve assembly allows for delivery of air from an air spring of the suspension system when the vehicle height is lowered. The vehicle height can be raised as an air compressor delivers actuating pressure through the valve assembly to the air spring. This may occur, for example, on vehicle start-up or when the vertical load on the vehicle suspension is increased. The valve assembly in an installation of this type normally is located in a receptacle in the end cap of the air spring. When it resides at that location, it is subjected to water and other contaminants, such as road salt, etc., that are present in the vicinity of the wheel well for the vehicle. It thus is necessary to provide protection of the solenoid valve assembly from the elements to resist contamination and deterioration of the valve assembly. The assembly also includes a mounting boss located at one axial end of the spindle. The boss is adapted to be fitted in an opening formed in a moulded receptacle that forms a part of the end cap of an air spring. A fluid fitting is preferably located at the end of the assembly opposite from the end location of the boss to permit a fluid connection between the outlet side of an air compressor and the inlet side of the solenoid valve assembly. In order that the invention may be well understood, there will now be described an embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which: FIGURE 1 is a cross-sectional assembly view of a solenoid valve assembly embodying the improvements of our invention; FIGURE 2 is a plan view of the assembly of Figure 1 showing the exterior of the encapsulation following the molding operation; FIGURE 3 is an end view of the assembly of Figure 2; FIGURE 4 is a subassembly view of the spindle that forms a part of the assembly of Figure 1; FIGURE 5 is a top view of the spindle shown in Figure 4 as seen from the plane of section line 5-5 of Figure 4; and FIGURE 6 is an end view of the spindle shown in Figure 5 as seen from the plane of section line 6-6 of Figure 5. The spindle of Figures 4, 5 and 6 comprises a cylindrical central portion 10 having a valve opening 12. Plastic ribs 14, 16 and 18 extend radially from the portion 10. Enlarged hub portion 20 is located at the right end of the cylindrical portion 10. It has a large diameter portion 22, a first small diameter portion 24 and a second small diameter portion 26. Circular ribs 28 surround the small diameter portion 26. At the left side of the rib 18, the spindle is formed with a reduced diameter portion 30. The reduced diameter portion 30 extends axially and defines an opening 32 adapted to receive an end of a pressure line, which will be described with reference to Figure 1. The spindle is formed of molded natural nylon, 30% glass-filled. After the molding operation, the molded part is removed and a bead of silicone material is deposited, as shown at 36, around the periphery of the reduced diameter portion 30, on the left side of the rib 18. A terminal support 38 extends radially from the spindle portion 10, as seen in Figure 4. As will be described with reference to Figure 1, the portion 38 is provided with openings that receive terminals for the electrical windings of a solenoid coil. The terminals are seen in Figure 6 at 40 and 42. As the bead of silicone is applied, as seen in Figure 5, silicone is applied also to the base of the terminals. After the terminals are installed, as seen in Figure 1, the spindle is wound with multiple windings 44 of copper wire of approximately 18 gauge. The wire is coated with an insulating shellac in the usual fashion. The ends of the windings are attached to the terminals, one end being soldered to one terminal and the other end being soldered to the other terminal. After the spindle is wound to form the solenoid coil, it is placed in a mold. The mold is designed with an interior cavity with dimensions that exceed the radial dimensions of the spindle and the windings. Heated nylon material is injected into the mold to form an encapsulation, as seen in Figure 1. The outer portion 46 of the encapsulation surrounds the windings of the coil, and the end portion 48 of the encapsulation surrounds the reduced diameter portion 30 of the spindle. The right hand end of the encapsulation defines a portion 50 that surrounds reduced diameter portion 26 of the boss 20. The encapsulating material, like the material of the spindle, is a natural nylon, 30% glass-filled plastic. As the encapsulating material flows under pressure into the mold, it compresses the silicone material thus forming a tight seal between the spindle and the silicone material. The silicone material also is compressed at the base of the terminals 40 and 42. As seen in Figure 1, a steel washer 52 is positioned between the ribs 16 and 18 prior to the encapsulation process step. A similar washer 54 is inserted around the reduced diameter portion 10 on the right side of the flange 14. The washers 52 and 54 form a part of the flux flow path for the solenoid valve assembly. A coil housing made of steel surrounds the windings. A metal solenoid core 56 is situated within the opening 12 in the central portion 10 of the spindle. The core is fixed with respect to the spindle and is provided with one or more grooves 58 extending axially from one end to the other. The right end of the fixed core 56 is received in a tubular guide 60 which is located within a cylindrical opening 62 in the boss 20. The right end of the opening 62 receives a cylindrical adapter 64 having an end opening 66 over which a screen 67 extends. The end 66 is received in a filter can 68, which contains filter foam material 70. The adapter 64 is secured to end tangs 74 on the boss 20. It is provided with radial openings 76 which receive retainer tabs 78 formed on the can 68 thereby holding the filter in place. The boss 20 is adapted to be received in a cylindrical opening in a molded receptacle at the end cap for the air spring of the suspension. O-ring seals 80 surround the reduced diameter portion 24 of the boss 20 to establish a seal. Figures 2 and 3 show the encapsulated assembly. The encapsulation provides a hermetic seal for the windings, the valve portions, the terminals and the washers 52 and 54. When the assembly is removed from the die, the core piece 56 is inserted, as shown in Figure 1. Prior to that step, a movable valve element 82 is inserted in the central opening of the spindle. The nose of the valve element 82 is provided with a tapered section 84 which is adapted to register with a conical surface 86 at the end of the central opening 32 described with reference to Figure 4. The valve element 82 is formed with a clearance with respect to the opening 12 in the spindle. A spring 90 located in spring pockets, formed in the valve element 82 and in the core piece 56, normally urges the valve element 82 in a left hand direction into registry with the orifice 88. A coupling sleeve 92 is received in the opening 32 as seen in Figure 1. An O-ring carried by the sleeve 92 is received in an annular groove in pressure line 94. The O-ring that registers with the annular groove is shown at 96. A screen element 98 is received in the opening 32 as seen in Figure 1. It is provided with a screen 100 at one end thereof. When the solenoid is energized, electromagnetic force causes the valve member 82 to shift in a right hand direction, thereby opening the orifice 88. This permits passage of air from the compressor, the outlet of which is connected to pressure line 94, through the orifice 88, past the valve element 82 and through the grooves 58 to the air spring side of the assembly. This raises the suspension. If the suspension is to be lowered, air may pass in the opposite direction through the orifice and through exhaust porting in the compressor as the compressor is deactivated. If the solenoid windings 44 are deenergized, the valve closes thereby maintaining a desired pressure in the air spring, which maintains the vehicle suspension at its proper height. After the terminals are inserted in the molded spindle and after the spindle is wound and soldered, the washers and the cover for the windings are installed. The cover, seen in Figure 1 at 102, is generally cylindrical and it surrounds the windings. It is provided with openings, as seen at 104 and 106 and 108. Thus, during the injection of the encapsulating material, the openings 104, 106 and 108 are filled with nylon. The nylon encapsulating material also flows around the reduced diameter portion 26 of the boss 20 surrounding the ribs 28. After the assembly is removed from the mold, the encapsulating material cools. Shrinkage occurs at this time. Because of the compression of the silicone material, the shrinkage of the encapsulating nylon material will not create an undesirable leakage point where the encapsulation material contacts the spindle material. Thus, the interior of the encapsulated assembly will not be exposed to water or other contaminants and the durability and operating reliability of the assembly is greatly enhanced. After the silicone sealant is applied, it is cured before the spindle is inserted into the mold. It is cured under ultraviolet light for one to two minutes. At that time, the sealant material turns from liquid form to a near solid state as molecular bonding occurs. The sealant material preferably is a silicone sealant manufactured by Loc Tite Corporation of Newington, Connecticut. It is referred to in the industry as NUVA-SIL sealant.

Claims: A solenoid valve assembly comprising a spindle (10) with a central opening (12), a movable valve element (82) in said opening (12), an electric coil (44) surrounding said central opening (12); a fluid fitting (32) at one end of said opening (12), a mounting boss (20) at the other end of said opening (12); a valve orifice (88) in said spindle (10) adapted to register with said valve element (82) when said coil (44) is deenergized said valve element (82) and said valve orifice (88) thereby providing controlled fluid flow through said central opening (12); and an encapsulation (46, 48, 50) enclosing said spindle (10); characterized in that a sealant material surrounds said spindle (10) and the encapsulation (46, 48, 50) compresses the sealant against said spindle (10), thereby hermetically sealing said coil (44). A solenoid valve assembly as claimed in claim 1, wherein said encapsulation (46, 48, 50) comprises a moulded nylon enclosure for said spindle (10) and said windings (44). A solenoid valve assembly as claimed in claim 1 or claim 2, wherein said sealant (10) is a silicone material. A solenoid valve assembly as claimed in any of the preceding claims, wherein said valve assembly comprises a pair of terminal extensions (40, 42) carried by said spindle (10), said coil (44) having ends connected to said terminal extensions (40, 42), terminal sealant material located at each of said terminal extensions (40, 42), said encapsulation (46, 48, 50) enclosing said terminal sealant material and compressing the same into sealing engagement with said spindle (10). A solenoid assembly as claimed in any of claims 1 to 3, wherein said coil (44) has at least one electric terminal (40, 42) extending to the exterior of said encapsulation (46, 48, 50), said terminal (40, 42) being surrounded by said sealant material, said encapsulation (46, 48, 50) compressing said sealant material against said terminal (40, 42) to effect a seal between said encapsulation (46, 48, 50) and said terminal (40, 42). A solenoid valve assembly as claimed in any of the preceding claims, further comprising a spring (90) contained within the central opening (12) which spring biases the valve element (82) into engagement with the valve orifice (88). A solenoid valve assembly as claimed in any of the preceding claims, wherein the orifice (88) has a conical surface (86) and the valve element (82) has a tapered section (84) which registers with the conical surface (86). A solenoid valve assembly as claimed in any of the preceding claims, wherein a solenoid core (56) is situated within the opening (12). A solenoid valve assembly as claimed in claim 8, wherein the core (56) is fixed with respect to the spindle (10). A process for manufacturing a solenoid valve assembly comprising moulding a spindle (10) from nylon material, winding electrical windings (44) around said spindle (10), enclosing said windings (44) in a housing (102); applying a silicone sealant in liquid form to said spindle (10) at one axial side of said windings (44); curing said sealant with ultraviolet light to harden the sealant; placing said spindle (10) and said windings (44) in a mould; injecting nylon material into said mould thereby surrounding said windings (44) and said spindle (10) with nylon and encapsulating said windings (44) and said spindle (10) upon injection of said nylon material into said mould as said nylon material compresses said sealant against said spindle (10). A process as claimed in claim 10, wherein said nylon material is natural nylon with approximately 30% glass filler. A process as claimed in claim 10 or claim 11, wherein the step of moulding said spindle (10) includes forming a flow restricting orifice (88) at the centre of said spindle (10), said valve assembly including a valve element (82) adapted to register with said orifice (88) whereby fluid flow through said orifice (88) is controlled as voltage is applied to said windings (44).

Inventors: BUTH MARTIN E, TENHUNDFELD STEVE, BUTH, MARTIN E., TENHUNDFELD, STEVE
Applicants: BORG WARNER AUTOMOTIVE, BORG-WARNER AUTOMOTIVE, INC.
Application year: 1994
Main classification: F16K31
IPC codes: H01F41, F16K31, F16F9, B60G17